Association of lactation with maternal risk of type 2 diabetes: A systematic review and meta-analysis of observational studies

Abstract

Aim: To investigate the association between lactation and maternal risk of type 2 diabetes, including a potential graded association according to lactation duration. Methods: A systematic review and meta-analysis of observational studies that investigated the reported association between lactation (irrespective of duration, intensity or mode) and maternal risk of type 2 diabetes was conducted. Results: A total of 22 studies (17 cohort studies and five cross-sectional studies) were included in this systematic review, and 16 contributed to the meta-analysis. Studies that investigated the association of lactation with risk of type 2 diabetes in the first months after birth in women with gestational diabetes reported conflicting results. Studies with a longer follow-up showed a graded protective association for lactation and the risk of type 2 diabetes, with a potentially larger risk reduction in women with gestational diabetes than in those without gestational diabetes. Overall, ever versus never lactation was associated with a 27% lower risk of type 2 diabetes (RR 0.73, 95% CI [0.65, 0.83]). Each additional month of lactation was associated with a 1% lower risk of type 2 diabetes (RR 0.99, 95% CI [0.98, 0.99]). However, the overall quality of the studies was modest. Conclusions: Lactation is associated with a significantly reduced risk of maternal type 2 diabetes over the life course, particularly in women with gestational diabetes. The protective effect seems to increase with longer duration of lactation. Further research is warranted to understand whether this association is modified by exposure to other risk factors.